mx1.osnow.de has no CNAME records.
Question and response
Question
dig mx1.osnow.de. NS
Answer
The response has no answer records.
Authority
osnow.de. 10331 SOA ns1.telekom-domains.de. dns.telekom.de. 2025121801 10800 3600 2419200 43200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0